The firing deck in a cylinder of an internal combustion engine is subject to great stresses created by intensive variations in temperatures to which they are subjected during operation of the engines. These stresses frequently cause distortion and/or cracking of the firing deck so that a new head is required or the cracks in the used head must be sealed and machined for reuse.
To preclude and/or minimize the foregoing problems, U.S. Pat. No. 2,949,901 discloses an insert removably seated in a recess in the firing deck area of the engine body, with clearance between the periphery of the insert and the peripheral wall of the recess. The exposed wall of the insert constitutes the firing deck and is subjected to at least the greatest heat generated during operation of the engine, but the insert is free to expand due to the peripheral clearance without subjecting the material of the engine body to undue stress.
Although the firing deck area can be located in the peripheral wall of a cylinder in some engines, in the normal engine the firing deck is in the end wall of the cylinder that is constituted by the surface of the engine head that is engaged with the engine block containing the cylinder.
According to the foregoing patent, the insert is secured by bolts or the peripheral portion of the insert is sandwiched between the engine head and block. While these inserts have been highly successful in precluding cracking of heads and prolonging the operational life of engines, extensive operation of the engines have resulted in some problems.
As an example of problems that have occurred, expansion of the insert is inhibited to some degree by location of the bolts which necessarily are spaced from the axis of the insert. In addition, excessive vibration of the engine can cause loosening of the bolts or over-torquing of the bolts upon insertion can create excessive stress on the head. Moreover, if the insert is secured only by being sandwiched between the head and body, repeated expansion and contraction of the insert, plus the vibration during operation of the engine, can cause migration of the insert toward a point of the cylindrical wall of the recess within which the insert is seated.